feat: Implement single-instance application and optimize window management

Add support for single instance applications to prevent multiple launches. Implement activation of existing instances through mutexes and window messages.
Optimize the management of the main window and add window message handling to respond to activation requests.

Author: sunquakes

App.xaml.cs

@@ -1,15 +1,61 @@
-using System.Configuration;
-using System.Data;
+using System;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
 using System.Windows;
+using System.Windows.Interop;
 using Application = System.Windows.Application;
 
 namespace DevTools
 {
-    /// <summary>
-    /// Interaction logic for App.xaml
-    /// </summary>
     public partial class App : Application
     {
-    }
+        private static readonly string MutexName = "DevTools_SingleInstance_Mutex";
+        private static System.Threading.Mutex? _mutex;
+
+        private const int HWND_BROADCAST = 0xffff;
+        private static readonly int WM_SHOWME = RegisterWindowMessage("WM_SHOWME_DEVTOOLS");
+
+        [DllImport("user32.dll")]
+        private static extern int RegisterWindowMessage(string message);
+
+        [DllImport("user32.dll")]
+        private static extern bool PostMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
+
+        [DllImport("user32.dll")]
+        private static extern bool SetForegroundWindow(IntPtr hWnd);
+
+        [DllImport("user32.dll")]
+        private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
+
+        private const int SW_RESTORE = 9;
 
+        public static int ShowMeMessage => WM_SHOWME;
+
+        protected override void OnStartup(StartupEventArgs e)
+        {
+            bool createdNew;
+            _mutex = new System.Threading.Mutex(true, MutexName, out createdNew);
+
+            if (!createdNew)
+            {
+                ActivateExistingInstance();
+                Shutdown();
+                return;
+            }
+
+            base.OnStartup(e);
+        }
+
+        private void ActivateExistingInstance()
+        {
+            PostMessage((IntPtr)HWND_BROADCAST, WM_SHOWME, IntPtr.Zero, IntPtr.Zero);
+        }
+
+        protected override void OnExit(ExitEventArgs e)
+        {
+            _mutex?.ReleaseMutex();
+            _mutex?.Dispose();
+            base.OnExit(e);
+        }
+    }
 }

MainWindow.xaml.cs

@@ -3,21 +3,12 @@
 using System.Drawing;
 using System.IO;
 using System.Reflection;
-using System.Text;
+using System.Runtime.InteropServices;
 using System.Windows;
-using System.Windows.Controls;
-using System.Windows.Data;
-using System.Windows.Documents;
 using System.Windows.Forms;
-using System.Windows.Input;
-using System.Windows.Media;
-using System.Windows.Media.Imaging;
-using System.Windows.Navigation;
-using System.Windows.Shapes;
+using System.Windows.Interop;
 using DevTools.Resources;
 using Application = System.Windows.Application;
-using MessageBox = System.Windows.MessageBox;
-using Button = System.Windows.Controls.Button;
 using ContextMenuStrip = System.Windows.Forms.ContextMenuStrip;
 using ToolStripMenuItem = System.Windows.Forms.ToolStripMenuItem;
 using ToolTipIcon = System.Windows.Forms.ToolTipIcon;
@@ -219,10 +210,27 @@ private void Window_Closing(object sender, System.ComponentModel.CancelEventArgs
 
         private void MinimizeToTray()
         {
-            _notifyIcon!.ShowBalloonTip(2000, Strings.Toolbox, Strings.MinimizedToTray, ToolTipIcon.Info);
+            _notifyIcon!.ShowBalloonTip(2000, Strings.Toolbox, Strings.MinimizedToTray, ToolTipIcon.None);
             Hide();
         }
 
+        protected override void OnSourceInitialized(EventArgs e)
+        {
+            base.OnSourceInitialized(e);
+            var source = PresentationSource.FromVisual(this) as HwndSource;
+            source?.AddHook(WndProc);
+        }
+
+        private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled)
+        {
+            if (msg == App.ShowMeMessage)
+            {
+                ShowWindow();
+                handled = true;
+            }
+            return IntPtr.Zero;
+        }
+
         protected override void OnClosed(EventArgs e)
         {
             _notifyIcon?.Dispose();